The present invention relates to a time setting system and a time setting method.
Content distribution services are known in which the use or reproduction, by users, of various kinds of content data such as software, movie data, and music data, for example, distributed via a network, is restricted with respect to time.
With these content distribution services, each user is able to select desired content data, download the selected content data, and reproduce the downloaded content data if it is before its expiration date.
In distributing content data such as music data and movie data via a network with restriction imposed on use or reproduction of the content, it is essential to control time between the destination (a client for example) of distribution and the source (a server for example) for the correct management of the expiration date of the content.
With related-art technologies, the NTP protocol (RFC1305: Internet <URL http://www.faqs.org/rfcs/rfc1305.html>) or the SNTP protocol (RFC1769: Internet CURL http://www.faqs.org/rfcs/rfc1769.html>) for example to provide time synchronization between the source and destination of distribution, thereby transmitting the time information of the distribution source for timing correct time to the distribution destination to set the time thereof to the time provided by the distribution source.
However, with the related-art technologies, if an illegal interference is made against the transmission of time information to delay the arrival of the time information at the destination of distribution, for example, a correct time setting cannot be provided due to the delay.